Tuning-control device



V. D. LANDON TUNING CONTROL vDEVICE prilv?, 1931.

3 Sheets-Sheet 1 Filed June l0, 1925 \7////./////// mm /J s D. w x y V x l wlT Essl-:5;

TTORNEY Filed Juri@ 1o, 1925 5 Sheets-Sheet 2 INVENTOR Ver/7m D. Landa/7.

WITNESSES: r

ATTORNEY April 7, 1931. v D. LANDON 1,799,983

TUNING CONTROL DEVICE Filed June l0, 1925 3 Sheets-Sheet 3 l'NvENToR Verna/7 mda/7.

Mv BY @www WITNESSES:

Patented Apr. 7, 1931 UNITEDv sfr-Aras PATENT OFFICE VERNON D. LANDON, OF EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOR- 'I'O NES-EING- HOSE ELECTRIC it IANUFACTURING COMPANY, A. CORPORATION OF PENNSYL- VAN IA TUNING-CONTROL DEVICE Application filed .Tune 10, 1925. Serial No. 36,105;

My invention relates to tuning systems for radio receiving apparatus. More speciiically, it relates to radio receiving sets in Which the tuning is to be performed as far as possible by a single manual control device.

Many attempts have been made to provide aradi-o receiving set having a plurality of tuned circuits all of Which may be simultane ously adjusted by a common control device.

i Heretofore, these attempts have not been successful, because the several tuned circuits -diiier in characteristics such as by small manufacturing variances. With such an arrangement, the same movement of the variable tuning device in each of several circuits will not produce the same change in the frequency in each of said circuits. Consequently, When the common control device, which may, for example, be the usual dial, is manipulated to bring one circuit to the correct frequency, the other circuits Will differ enough from that frequency to prevent the efficient operation of the receiving set.

A regenerative detector adds greatly to the sensitiveness of areceiving set, but its use is open to the objection that, in the hands of an unskilled operator, it produces radiations Which disturb listeners using other receiving sets in the neighborhood. It has been proposed to remedy this by inserting one or more stages of tuned radio-frequency ampliiication` between the antenna circuit and the regenerative detector. This arrangement has the disadvantage that the operator is required to tune the stages of the amplifier and the oscillating cir-cuit of the regenerative detector simultaneously.

In many receiving sets, the operator is thus required to manipulate three or more dials concurrently. A very small departure of any one of these dials from the positionl which corresponds exactly to theV position of the other dials frequently causes the operator to fail te obtainl a signal, although the signal could'be received if the receiver were properly tuned. If the several dials, or the reactors connected thereto, be mechanicallyl united so that one control moves all of them, thedifficulty is not removed because the divergencies amongv the several circuits may prevent the operator from discovering that the signal is present. Y

With a regenerative detector, the presence of a signal is most readily discovered by means of the beat-note occasioned when the oscillating circ-uit of the detector is nearly, but not exactly, in tune With the signal. If

, a radio-frequency amplifier is between the receiving circuit and the regenerative detector, even this very sensitive Way of discovering the presence of the signal will fail when the amplifier is not as nea-r, or at least almost as near, to the correct tuning as the detector.

It is an object of this invention to provide a receiving set in Which theV presence of a signal, may be discovered by means Aof a non-reradiating beat note Without requiring the operatorl to manipulate more than one control at a time. Y

It is a further object of this invention to provide acommon control for a plurality of tuned circuits, and to` supplement said control by means for correcting the divergencies of the several circuits from the frequency of some one circuit.

It is a further object of this invention to provide a receiving set, comprising a tuned. radio-frequency multi-stage amplifier and a regenerative detector, with means whereby the multi-stage .amplifier may be kept at all times suiiiciently near the tuning of the oscillating circuit in the detector to ensure that a beat-note will be heard Whenever a signal of the frequency corresponding to the tuning of the detector is present. Y

` It is a still further object of this invention to provide an independentv control of the degree of regeneration in' the detector;

It is a further object of this invention to provide means by which the approximate tun` ing of the several. circuits of the .amplifier by the common control may be supplemented to bring each of the amplifier circuits to the exact tuning desired. y

It is a further object of my invention to increase the distancebetween the coils carrying radioffrequency current Without increasing the dimensions of the cabinet.

Itis a further object of' my invention to -soarrange the direction and location of the i several radio-frequency coils that electromagnetic induction between them is avoided. The position of these coils within the cabinet, chosen to further the objects already recited, renders it impossible to accomplish this object either by the familiar' oblique arrangement of the coils in a row, resembling a flight of steps or by the arrangement of them in a row with their axes mutually perpendicular.

It is a further object of my invention to locate the tubes in which only audio frequency is present between the tubes having radio frequency, whereby the coils carrying radio frequency may be separated from one another without necessitating long conductors between coils and tubes and without wasting space within the cabinet.

Other and further objects of the invention will he apparent from the following detailed description and the accompanying drawings in which Figure 1 is a front view of a preferred forni ol' apparatus, embodying my invention,

Fig. 2 is a view in section on the line I--ll of Fig. 1,

Fig. 3 is a view III-IH of Fig. 2,

Fig. 4 is a circuit diagram, and

Fig. 5 is a perspective view of a detail.

Referring to Fig. 4, the apparatus is provided with the usual antenna 1 and ground connection 2. An inductor 3 is inserted between the antenna and the ground connection. By means of an adjustable connection 4, any predetermined portion of the inductor 3 mav in section on the line be included in the .antenna circuit. Preferably, the adjustment of this connection is possible only by opening thev cabinet. It is intended that this adjustment shall be made when the set is first put into operation and not disturbed afterwards. lt will be unnecessary to change this adjustment unless a different antenna is substituted.

The inductor 3 is inductively coupled to a coil 5 which, together with an adjustable condenser 6 constitutes the tuned circuit of the first stage of a radio-frequency amplifier. This stage comprises the usual connections to a vacuum tube device 7. The position of the tube is indicated in Fig. 3 by marking the sockets which receive the terminal pins of the tubes with the legend tube 7. The location of other tubes mentioned below is similarly indicated. The connections to the tube 7 include a neutralizing condenser 8 and a connection 9 from the cathode to the mid-point of the coil 5.

The connection 9 and the condenser 8 cooperate to prevent undesirable consequences of the capacity between the grid and the plate in the tube 7, as explained in the patent to Rice, 1,334,118, issued, March 16, 1920.

rlhe output circuit of the tube 7 includes the primary 11 of a transformer. The second ary l of this transformer cooperates with an adjustable condenser 13, forming the tuned Circuit of the second. stage of the ampli lier. This stage includes connections to the tube 14 which are like the connections to thle tube 7, except that the cathode-heating circuit of the tube 7 includes a resistor 15 in addition to the resistor 16, which is common to all the cathode-heating circuits.

rl`he output circuit of the tube 14 includes the primary .17 of a transformer, the secondary ll of which cooperates with an adjustable condenser 19 to constitute the oscillating or tuned circuit forming part of the grid circuit of a regenerative detector.

rThe regenerative detector is preferably of the usual construction, including a vacuum tubr- QC', the plate circuit of which includes a fielder coil 2l and the primary 22 of an audiofrcfpuuicy transfm-nier 23. for adjusnient of the coupling between thc ticlaler coil il and the coil 18 in the grid circuit of the tube 20. This grid circuit also Vincludes the usual grid biasing device comprising a condenser and a grid leak 25.

The secondary 2G of the audio-frequency transformer 23 is included in the grid eircuit of a tube 9.7 which constitutes the first audio-frequency amplifier. lVhen it is desired to use but one stage of audio-frequency amplifier, the telephone is attached at the terminals 2S, which are included in the plate circuit of the tube 27.

In parallel to the terminals 28 is the primary 31 of a second audio-frequency transformer 30, the secondary win ding 32 of which is in the grid circuit of a vacuum tube 33, which constitutes a second audio-frequency amplifier. The plate circuit of the tube 33 i11- eludes the terminals 34 to which the telephone may be attached.

A. battery A supplies the several filamentary cathodes in parallel, the rheostat 1G controlling the current and therefore the temperature for all of these cathodes except the cathode of the tube 7. The rheostat 15 being in series with the rheostat 16 makes it possible to maintain the cathode of the device 7 at an adjustable temperature below that of the other cathodes.

The battery B is provided with taps by means of which different voltages may be impressed upon the several tubes. The whole of this battery is included in the plate circ-uit of the tube 33. A somewhat smaller portion of the battery B is included in the plate circuits of the two radio-frequency ampli- 7 and 14 and a still smaller portion is included in the plate circuit of the detector 21. The several tubes are thus supplied with their appropriate plate potentials.

Two C batteries C and C1 are provided. By this means, a small grid-biasing potential is impressed upon the first audio-frequency amplifier and a larger grid-biasing poten- Provision is made lll) tial upon the second audio-frequency ampli- `lier. It will, therefore, be evident that all of the adjustments usually required inv a receiving` set of this kind are possible.

.Referring now to Figs. 1 and 3, the condensers 6, 13 and 19 are preferably mounted in a rou1 along't-he panel 41 of the cabinet in Vwhich the receiving set is housed. Preferably they are each in theV form of a stator and a rotor, the several rotors being mounted each upon its shaft. The shaft 50, whichcarries the rotor 51 of the condenser 6, is mounted in the end plates52 of the condenser that are securedto the panel 41. A milled Wheel 53 is mounted on one end of the shaft 50 and projects through the panel 41. A drum 54 is secured to the Wheel 53 upon the face opposite the condenser 6. The

through thepanel'41.

Vthe Wheel 81.

drum is preferably ofmaterial upon which pencil markings can be made and it shows through an opening 55 inthe panel 41. The opening is surrounded by an esoutcheon plate 56 carrying a reference mark 57.

The rotor of the condenser 13 is mounted on a sha ft 58 which preferably turns in hear ings in the end plates of the condenser 13, which end plates are mounted on the panel 41. The end of the shaft 58 nearest the wheel 53 is provided with a crank arm 61. The end of the crank arm farthest from the shaft extends parallel to the shaft into a slot 62 in the body of the Wheel 53.

At the other end, the shaft 58 is provided with a milled wheel 66 which also projects This wheel has a drum 67 which shows through the opening 68 in an escutcheon plate 69. The wheel 66 is provided with a slot 71 which is shorter than the slot 62 in the wheel 53 The rotor of the condenser 19 is mounted on a shaft 72,`Which turns in the end plates of the condenser, which are also secured to the panel41. The end of the shaft 7 2 nearest the shaft 58 is provided with a wheel 73 v., which projects through the panel 41. The

wheel 7 3 has a drum 74 toward the drum 67. This drum shows through an opening 'Z5 in the escutcheon plate 69. A portion of the escutcheon plate, extends between the open-V ings 68 and 75 and is provided with a reference mark 76. A rod 77 is secured to the Wheel 73 and extends into the slot 71 in the wheel 66 to provide a lost-motion connection between the shafts 58'and 72.

The tickler coil 21 is mounted on a face of the milled' wheel 81 the edge jects through the panel-41.4 On the face of the milled wheel 81, opposite that carrying the coil 21, the Wheel is provided with a drum 82, which shows through an opening 83 inthe escutcheon plate 84, that carries a reference mark 8,5. The coil 21 is not concentric with p If the coil overlaps the center of the Wheel 81, the shaft 86 upon which this wheel is mounted, will be made'shortei" coil 18 that of which propossible,'with its axis in The coil 18 is mounted close to the coil 21V and with its axis parallel to the shaft 86 but not' in alinement therewith.V The relative position of the coils 18 and 21 is such that as the wheel 81 is rotated, these coils overlap Vto a varying extent, but never entirely cease lo overlap.

In the position of the wheel 81, in which the coil 21 overlaps the coil 18 least, the mutual inductance of the two coils is nearly zero. In the position of the Wheel 81 Aillustrated in Fig. 3, which is 180 away from the position of least overlap, as illustrated in Figs. 1 and 5, the coil 21 is preferably concentric with the coil 18 and the mutual inductance between these coils is a maximum. Preferably, the relative position and the diameter of the two coils are so chosen that the mutual inductance does not change sign during the movement of the wheel 81.

If desired, the wheel 81 may be provided with stops to prevent motion through more than 180, but the stops are not necessary, for the mutual inductance varies between zero and themaximum, regardless of `whetherthe wheel is turned through 180 or more.

The constants of the circuits 5-6, 12-13 and 18-19 are'so chosen that when all three condensers are moved simultaneously by rotating the wheel 53, the frequency of the circuit 5-6 will differ from the circuit 18-19 in the same direction that the frequency of the circuit 12-13 differs from the frequency of the circuit 18-19.

The axis of the coil 18 is parallel to thc length of the cabinet. In order that it may cooperate with the coil 21 carried by the wheel 81, it is mounted above the tube-supporting shelf and toward the rear of the cabinet. The coils 5 and v12 are placed below the shelf and toward the forward part of the cabinet at one side of the transformers 23 and 30. This results in a compact structure but requires peculiar'directions of the axes of the coils 5 and 12 to obtain zero coupling when the coils are thus located.

Ordinarily coil 12 would have its axis parallel to the axis of coil 18 and its'centerwould be located so far to one side of the axis of the flux, from the coil 18 would be parallel to the turns of the windings of coil 12.

I have discovered a method of locating the coil 12 which secures the advantages of the ordinary method and leaves t-he coil near the tube 14 and condenser 13. The coil is located as near these elements as conveniently the plane including the axis of the coil 18 and perpendicular to the flux from coil 18 at said location.

Tlie'axisof coil 12 is-not parallel to 'the vaxis of coil 18 but they converge toward the the frequency of :1

This is because coil 12 is nearer the axis (prolonged) of coil 18 and farther from coil 18 itself than is usual. The axis of coil 1Q, is not only at an angle to the horizontal but also at an angle to the plane of the paper in Fig. 3 because the plane through the axes of coils 12 and 18 is oblique.

The coil 5 is located close to tube 7 and condenser G. Its aXis is at right angles to the plane of the axes of coils 12 and 18, consequently no flux from either of these coils can affect coil 5.

The coils 5, 12 and 18 are, therefore, so placed that there is zero coupling between them and each is near the tube to the grid of which it is connected and near the condenser which tunes the grid circuit of that tube. Moreover', these features of the location of the coils have been accomplished without adding to the size of the cabinet.

In the operation of the device, the operator turns the wheel 81 to a position in which the coupling between the coils Q2 and the coil 18 is close. I-Ie then turns the wheel 58 continuously in one direction until a beat-note is heard in the telephone. The frequency of the circuit 18-19 will be nearly like the frequency of the incoming signal, when the beatnote occurs. The operator may continue to turn the wheel 53 in the same direction until the beat-note reaches a low pitch. If he goes beyond this point, it will be more convenient to adjust the condenser 19 directly by the wheel 7 3.

An operator need acquire but little skill. in order to keep this reverse movement of the wheel 73 slight. No, harm however results if it be large. The reverse movement of thc wheel 73 turns all the wheels backward beright in Fig. 8.

Vcause during the forward movement of the 61 and the shaft 77 62 and 71,

wheel 58 the crank arm reached the rear ends of the slots respectively.

If the operator moves the wheel 73 back too far, causing the pitch of the note in the telephone to rise again, he may correct it by again moving the wheel 53 forward, For a very slight correction, he may move the wheel 7 8 if preferred.

The beat-note having been brourht to its lowest pitch or silenced. the operator turns the wheel 81, thereby adjusting` the coupling between the coils 18 and 21 to the point where the best results are obtained. This is the point where the tube 20 is almost but not quite oscillating. It is easy to recognize this position by a characteristic sound in the telephone which can be heard just as the coil 21 passes through this position while the coupling is being increased.

The operator then moves the wheels 53 and 66 until'the signal comes in with maximum volume.` The first movement of either 'of these wheels should be backward but if they are-moved in the vWrong direction or moved too far, the re-appearance of the beatnote makes the operator aware of his error. Consequently, no great skill is required to operate the device. Even in the hands of an unskilled operator tuning is accomplished easily and quickly.

When the proper position of the several wheels for best reception of signals from a given station has been found, marks are made on the drums 54T, 67, 7 4 and 82 opposite the reference marks 57 7 6 and 85. When desiring to listen to these signals again, it is only necessary to bringl the marks on the drums opposite thc reference marks.

Although I have illustrated and described in detail a single form of my invention, it will be evident to those skilled in the art that my invention is capable of being embodied in many forms. I therefore do not desire to be limited beyond the limits required by the prior art and expressed in. the accompanying claims.

I claim as my invention:

1. In a radio device, a plurality of tuned circuits, each including a variable reactor, means for varying one of said reactors to tune its circuit to a predetermined frequency, said means acting simultaneously on thc other reactors to tune their circuits to frequencies nearly equal to and always on the same side of said predetermined frequency, said means being adapted for thereafter independently adjusting said reactors.

2. In a radio device, a plurality of tuned circuits, each including a variable reactor, means for varying one of said reactors to tune its circuit to a predetermined frequency, said means acting siniultaneously on thc other reactors, all'in thc same direction, to tune their circuits nearly to said predetermined frequency, the respective differences between the tuning of said other circuits and said predetermined frequency being all in thc same sense, and means for separately acting on each of said other reactors oppositely to said direction to tune all the circuits alike.

3. In a radio device, a plurality of tuned circuits, means for varying the tuning of each circuit, mechanism connecting said means, said mechanism including lost-motion devices, whereby one of said circuits may be tuned to a predetermined frequency and the other circuit simultaneously tuned to frcquencies differing therefrom.

il. In a radio device, a plurality of tuned circuits, means for varying the tuning of each circuit, mechanism for connecting said means including lost-motion devices, whereby one of said circuits may be tuned to a predetermined -frequency and the others simultaneously tuned to frequencies differing therefrom, and means cooperating with said lostmotion devices for individually tuning each of said other circuits to said predetermined frequency.

5. In a radio receiving set, a plurality of amplifiers in cascade relation, a tuned circuit associated with each amplifier, a regenerative detector supplied by the last amplifier, a tuned circuit associated with said detector, means for adjusting the tuning of said detector-circuit, and means operatively associated with said adjusting means for simultaneously adjusting the amplifier-circuits to a tuning diifering in predetermined amounts from that of the detector-circuit and means for correcting said difference in the tuning of each of the amplilier circuits.

6. In a radio receiving set, a plurality of amplifiers in cascade relation, tuned circuits, one associated with each amplifier, a regenerative detector, a tuned circuit associated with said detector, means for adjusting the tuning of said detector-circuit, means operatively associated with said adjusting means for simultaneously adjusting the amplier-circuits to a timing differing in predetermined amounts from that of the detector-circuit, means for correcting said difference in the tuning of each of the amplifier circuits, and independent means for adjusting the degree of regeneration.

7. In a radio tuning device, a series of adjustable circuit-elements, a succession of shafts, one actuating each circuit-element, a lost-motion connection between each of said shafts and the neXt, and manual means for actuating the respective shafts.

8. In a radio tuning device, a plurality of variable condensers, each comprising a stator and a rotor, a common support for the stators of said condensers, bearings carried by said support, a shaft for each of said rotors mounted in said bearings, means for actuating the respective shafts and lost-motion connections between the successive shafts.

9. In a radio tuning device, a plurality of variable condensers each comprising a stator and a rotor, a common support for the sta- 'tors of said condensers, a row of bearings carried by said support, a series of alined shafts, one for each of said rotors, mounted in said bearings, means extending through said support for actua-ting the respective shafts and lost-motion connections between successive shafts, additional bearings also carried by said support, a variable coupling having a movable part, a shaft for said movable part mounted in said bearings, and independent means for actuating said last named shaft.

l0. In a radio tuning device, a plurality of variable condensers each comprising a stator and a rotor, a common support for the stators of said condensers, a row of bearings carried by said support, a plurality of alined shafts, one for each of said rotors, mounted in said bearings, means extending through said support for actuating the respective shafts and lost-motion connections between 

